AT72ED 72mm f/6 ED doublet refractor, white and gray tube

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This Astro-Tech ED refractor has:

• 72mm f/6 fully multicoated ED doublet refractor optics
• dual-speed rotating 2” Crayford focuser with 10:1 ratio fine focusing
• 2” and 1.25” non-marring compression ring accessory holders
• combined dovetail/tripod bracket for use on a photo tripod or a German equatorial mount
• retractable self-storing lens shade
• amazing wide field astrophotographic capabilities
• long-lasting white paint finish with hard anodized gray trim
• aluminum-frame foam-fitted hard case
• two-year warranty

Astronomy magazine called this scope’s predecessor, the 66mm Astro-Tech AT66ED, “a product everyone should own.” The new Astro-Tech AT72ED upgrades that best-selling predecessor by increasing the aperture to 72mm to give you 9% higher resolution and 19% more light gathering; upgrades the focuser to 2”, with a 1.25” adapter; and increases the focuser travel to 80mm to allow imaging with a wider variety of camera types. Astronomy said the AT66ED was “a great grab-and-go scope, a fine little astrograph, a super-finder scope, and a daytime spotting scope.” The same is equally true for the new AT72ED.

The images from the 430mm f/6 ED air-spaced doublet optics of this Astro-Tech AT72ED refractor are virtually free from spurious color (chromatic aberration), even at high magnifications. At its low price, the optical performance is little short of astonishing. The exceptional AT72ED optics are even more impressive when you consider the package they come in. The finely-machined scope has a dual speed 2” Crayford-style focuser with a microfine 10:1 fine-focusing ratio. You can rotate the focuser a full 360° to put your eyepiece or camera in the most comfortable observing position. The supplied 2” and 1.25” eyepiece adapters use non-marring brass compression rings that won’t scratch your eyepiece and accessory barrels. The Astro-Tech AT72ED has a retractable lens shade and comes in a locking aluminum-frame hard carrying case.

This 12” long refractor optical tube (14.5” long with the lens shade extended) has the right balance of aperture and focal length to use as a low-power rich field telescope, as a medium-power planetary telescope, or as any kind of telescope in between. Its compact size, light weight, and convenient removable L-shaped mounting foot that mounts on any photographic tripod also make it an excellent terrestrial spotting scope for vacations, birding, or nature studies. In addition, optional camera adapters turn the AT72ED into a superb 430mm (8.6x) f/6 daytime telephoto lens and nighttime wide-field astrograph, as can be seen in the feature image section below. The tripod mounting foot is also a dovetail adapter that fits directly into the dovetail slot on the top of many altazimuth and German equatorial mounts, such as those from Astro-Tech, Celestron, Meade, and Vixen.

The AT72 image of M31, the Andromeda Galaxy, shown in the feature image section below is by Tibor Mihalovits. He was happy to share the image with us because, as he said, “I'm at the very beginning on my astrophotography adventure and it is a good example for people trying to start out to see what the AT72ED can do with an unmodified Canon EOS Rebel T1i DSLR camera in 90 minutes. With the AT72ED, you don't have to spend $5000 on a single scope to get something nice! Since I got the AT72ED, I've been recommending it on the Cloudy Nights imaging forum a lot for the guys that want to start out. You just can't beat that scope, price, quality, aperture. My next imaging scope will be an A-T scope also! Thank you!”

Features of this Telescope . . .

  • ED doublet refractor optics: 72mm (2.83”) aperture, 430mm focal length, f/6 focal ratio air-spaced doublet lens using premium Ohara glass from Japan, including an ED (Extra-low Dispersion glass) element to reduce spurious color halos and fringing to vanishingly low levels. While we do not claim fully apochromatic performance in the class of a multiple thousand dollar Takahashi, Astro-Physics, or TMB refractor, the AT72ED is so free from spurious color as to be virtually indistinguishable from an apochromatic system. And, as Mr. Spock probably said in one episode of Star Trek or another, “Any difference that makes no difference, is no difference.”

  • Multicoated optics: The objective lens has the latest state-of-the-art broadband antireflection multicoatings on all four air-to-glass surfaces for high light transmission and excellent contrast. This can easily be seen by looking into the objective lens of the scope. Virtually no reflection of your face will be seen. It’s a sure sign that the high transmission coatings are doing their job, by letting virtually all the light enter the scope, rather than reflecting some light back to your eye.

  • Internal light baffles: There are three contrast-enhancing knife edge baffles inside the optical tube, and anti-reflection threading the full length of the focuser drawtube, for truly dark sky backgrounds and high terrestrial contrast. In addition, the edges of the objective lens are blackened to eliminate contrast-reducing stray internal reflections.

  • Full power range capability: The “highest useful magnification” listed above right is 143x. This is the power obtained with a 3mm eyepiece, which provides an exit pupil of 0.5mm (about 1/50th of an inch) and 51x per inch of aperture. This is generally the smallest exit pupil recommended with any telescope before the images start to become too dim to be consistently useful.
    Higher powers are possible for lunar and planetary observing, however, given excellent seeing conditions, although the increasing dimness of the image will start to limit the performance on all but the brightest objects.
    The lowest useful power is 11x, achieved with a 40mm eyepiece (a 40mm 1.25” TeleVue Plössl will give you a 4.2° field at that power; while a 2” Astro-Tech 40mm Titan Type II ED will give you a 6.33° field). At 3.8x per inch of aperture, this is very close to the 4x per inch of aperture generally regarded as the lowest practical power with any telescope. A 40mm eyepiece on the AT72ED will give you a 6.67mm exit pupil, larger than most eyes can dilate. Any lower power would simply waste some of the scope’s light gathering capacity, as its collected light would fall on your iris, rather than entering your eye.

  • Dew shield: A self-storing retractable dew shield slows the formation of dew on the lens in cold weather to extend your undisturbed observing time. It also improves the contrast, similar to the effect of the lens shade on a camera lens, when observing during the day or when there is excessive ambient light at night, such as a neighbor’s backyard security light.

  • Dual speed microfine 2” Crayford focuser with 1.25” adapter: The precision-made 2” focuser has dual-speed focusing. There are two coarse focusing knobs. The right knob also has a smaller concentric knob with 10:1 ratio reduction gear microfine focusing. This provides exceptionally precise image control during high power visual observing or critical DSLR or CCD imaging. The focus knobs have knurled rubber and ribbed gripping surfaces so they are easy to operate, even while wearing gloves or mittens in cold weather. The 80mm (3.15”) travel focuser drawtube has a scale marked in 1mm increments so you can note individual focuser positions for easy return to the correct focus when switching between visual use and photography. A lock knob under the focuser lets you lock in your photographic focus.
    The focuser drawtube terminates in a 2” compression ring accessory holder to accept a 2” star diagonal and 2” photo accessories. A lock knob on the top of the scope allows the focuser to be rotated a full 360°. This lets you rotate the focuser to line up a camera in either a landscape or portrait orientation (or any orientation in between), as well as put a star diagonal and eyepiece into the most comfortable observing position, and then temporarily lock the focuser in that position.
    The supplied 1.25” accessory adapter slips onto the 2” accessory holder and uses a soft brass compression ring to hold 1.25” star diagonals and photo/visual accessories in place. The 1.25” and 2” compression rings won’t scratch the barrels of your star diagonal or accessories as an ordinary thumbscrew can.

  • Combined equatorial dovetail/tripod adapter: The AT72ED has a removable L-shaped dovetail mounting foot/tripod adapter. The 1.75” wide x 3.25” long mounting foot is sized and shaped (with slanted sides) to fit the Vixen-style dovetail slot on the head of many altazimuth and equatorial mounts. It will fit, without modification, the Astro-Tech Voyager altazimuth mount and the Celestron CG-5 and Advanced Series, Meade LXD-75, and Vixen Great Polaris German equatorial mounts, among others.
    In addition, the mounting shoe has two 1/4”-20 thread mounting holes that allow it to be installed on any camera tripod that has a standard 1/4”-20 thread mounting bolt. You can choose the mounting hole that provides the best balance when used with your particular combination of star diagonal, eyepiece, and/or camera.
    Cork pads on the underside of the mounting shoe help keep the scope from swiveling when mounted on a photo tripod. The dovetail is removable to allow the AT72 to be used with optional guidescope rings as a photoguide for a larger telescope.

  • Tube finish: The optical tube is finished in a durable white automotive-grade paint with black trim and a gray and black anodized focuser.

  • Other supplied accessories: A slip-on metal dust cap is standard. Two threaded holes for installing a finderscope mounting bracket are located on the upper left side of the scope body. One hole keeps the finder in a fixed position relative to the scope’s mounting foot, regardless of how the focuser is rotated. The other rotates with the focuser, keeping the finder in the same position relative to the focus knobs, again no matter how the focuser is rotated.

  • Shipping/storage case: The scope comes in a 15.5” x 10” x 7.5” aluminum-frame locking hard case with carry handle. The foam-fitted case has cutouts for the scope, a 1.25” or 2” star diagonal, and up to three eyepieces (two 1.25” and one 2”).
    Astro-Tech is one of the very few manufacturers to provide a case at no charge for protection during shipping and as a storage convenience when the scope is not in use. Unfortunately, FedEx, UPS, and the Postal Service are very good at treating packages roughly. Occasionally, your scope can arrive in perfect condition, but with the walls of the shipping case dented in transit from rough handling, or the aluminum frame sprung, rendering the appearance of the case less than pristine. Damage to the shipping/storage case in such instances is not covered by warranty.

  • Two year warranty: As an expression of the confidence Astronomy Technologies has in the quality of their products, the Astro-Tech AT72ED is protected by a two-year limited warranty against flaws in materials and workmanship (shipping case excluded).
Highest Useful Magnification:
This is the highest visual power a telescope can achieve before the image becomes too dim for useful observing (generally at about 50x to 60x per inch of telescope aperture). However, this power is very often unreachable due to turbulence in our atmosphere that makes the image too blurry and unstable to see any detail.

On nights of less-than-perfect seeing, medium to low power planetary, binary star, and globular cluster observing (at 25x to 30x per inch of aperture or less) is usually more enjoyable than fruitlessly attempting to push a telescope's magnification to its theoretical limits. Very high powers are generally best reserved for planetary observations and binary star splitting.

Small aperture telescopes can usually use more power per inch of aperture on any given night than larger telescopes, as they look through a smaller column of air and see less of the turbulence in our atmosphere. While some observers use up to 100x per inch of refractor aperture on Mars and Jupiter, the actual number of minutes they spend observing at such powers is small in relation to the number of hours they spend waiting for the atmosphere to stabilize enough for them to use such very high powers.
143x
Visual Limiting Magnitude:
This is the magnitude (or brightness) of the faintest star that can be seen with a telescope. The larger the number, the fainter the star that can be seen. An approximate formula for determining the visual limiting magnitude of a telescope is 7.5 + 5 log aperture (in cm).

This is the formula that we use with all of the telescopes we carry, so that our published specs will be consistent from aperture to aperture, from manufacturer to manufacturer. Some telescope makers may use other unspecified methods to determine the limiting magnitude, so their published figures may differ from ours.

Keep in mind that this formula does not take into account light loss within the scope, seeing conditions, the observer’s age (visual performance decreases as we get older), the telescope’s age (the reflectivity of telescope mirrors decreases as they get older), etc. The limiting magnitudes specified by manufacturers for their telescopes assume very dark skies, trained observers, and excellent atmospheric transparency – and are therefore rarely obtainable under average observing conditions. The photographic limiting magnitude is always greater than the visual (typically by two magnitudes).

11.8
Focal Length:
This is the length of the effective optical path of a telescopeor eyepiece (the distance from the main mirror or lens where the lightis gathered to the point where the prime focus image is formed). Focallength is typically expressed in millimeters.

The longer the focallength, the higher the magnification and the narrower the field of viewwith any given eyepiece. The shorter the focal length, the lower themagnification and the wider the field of view with the same eyepiece.

430mm
Focal Ratio:
This is the ‘speed’ of a telescope’s optics, found by dividing the focal length by the aperture. The smaller the f/number, the lower the magnification, the wider the field, and the brighter the image with any given eyepiece or camera.

Fast f/4 to f/5 focal ratios are generally best for lower power wide field observing and deep space photography. Slow f/11 to f/15 focal ratios are usually better suited to higher power lunar, planetary, and binary star observing and high power photography. Medium f/6 to f/10 focal ratios work well with either.

An f/5 system can photograph a nebula or other faint extended deep space object in one-fourth the time of an f/10 system, but the image will be only one-half as large. Point sources, such as stars, are recorded based on the aperture, however, rather than the focal ratio – so that the larger the aperture, the fainter the star you can see or photograph, no matter what the focal ratio.

f/6
Resolution:
This is the ability of a telescope to separate closely-spaced binary stars into two distinct objects, measured in seconds of arc. One arc second equals 1/3600th of a degree and is about the width of a 25-cent coin at a distance of three miles! In essence, resolution is a measure of how much detail a telescope can reveal. The resolution values on our website are derived using the Dawes’ limit formula.

Dawes’ limit only applies to point sources of light (stars). Smaller separations can be resolved in extended objects, such as the planets. For example, Cassini’s Division in the rings of Saturn (0.5 arc seconds across), was discovered using a 2.5” telescope – which has a Dawes’ limit of 1.8 arc seconds!

The ability of a telescope to resolve to Dawes’ limit is usually much more affected by seeing conditions, by the difference in brightness between the binary star components, and by the observer’s visual acuity, than it is by the optical quality of the telescope.

1.61 arc seconds
Aperture:
This is the diameter of the light-gathering main mirror or objective lens of a telescope. In general, the larger the aperture, the better the resolution and the fainter the objects you can see.
2.83"
Heaviest Single Component:
The weight of the heaviest component in this package.
5 lbs.
Telescope Type:
The optical design of a telescope.  Telescope type is classified by three primary optical designs (refractor, reflector, or catadioptric), by sub-designs of these types, or by the task they perform.
Refractor
 
Based on Astronomy magazine’s telescope "report cards", scopes of this size and type generally perform as follows . . .
Terrestrial Observation:
Observing terrestrial objects (nature studies, birding, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial observing. Scopes with apertures under 5" to 6" are generally most useful for terrestrial observing due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes. 
Yes
Lunar Observation:
Visual observation of the Moon is possible with any telescope. Larger aperture scopes will provide more detail than smaller scopes, thereby getting a higher score in this category, but may require an eyepiece filter to cut down the greater glare from the Moon's sunlit surface so small details can be seen more easily. Lunar observing is more rewarding when the Moon is waxing or waning as the changing sun angle casts constantly varying shadows to reveal craters and surface features by the hundreds.  
Good
Planetary Observation:
Good
Binary and Star Cluster Observation:
Fair
Galaxy and Nebula Observation:
Fair
Photography:
Yes
Terrestrial Photography:
Photographing terrestrial objects (wildlife, scenery, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial photography. Scopes with focal ratios of f/10 and faster and apertures under 5" to 6" are generally the most useful for terrestrial photography due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes.
Yes
Lunar Photography:
Photography of the Moon is possible with virtually any telescope, using a 35mm camera, DSLR, or CCD-based webcam (planetary imager). While an equatorial mount with a motor drive is not strictly essential, as the exposure times will be very short, such a mount would be helpful to improve image sharpness, particularly with webcam-type cameras that take a series of exposures over time and stack them together. Reflectors may require a Barlow lens to let the camera reach focus. 
Yes
Planetary Photography:
Yes
Star Cluster / Nebula / Galaxy Photography:
Yes
Warranty:
1 year
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Overall Product Rating: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics(4.75)   # of Ratings: 4   (Only registered customers can rate)

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1. Robert on 5/20/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
This scope is a nice balance of performance, price, size, and weight. It isn't a perfect APO, but it's close. I can't detect any purple haze at all anywhere in the FOV and only a slight amount of bright purple/yellow lateral color on the limb of the moon at the very edge of super and ultra wide field eyepieces at low powers. This effect is not visible in 60 degree or narrower fields of view. I have taken this scope up to about 125x without any noticeable image breakdown. It is still sharp, contrasty, and color-free in the center. The image seems almost reflector-like except better because there is no central obstruction, spider-vane spikes, or tube currents. Saturn looked textbook perfect, though its moons were difficult to pick out, probably due to limited aperture and magnification.

The stars are pinpoint sharp throughout the field, though refocusing is necessary due to extreme curvature of field due to the short focal length and being a refractor without a field flattener. I'd say at lowest power I have to shift focus 5mm to 10mm for ultrawide fields from center to edge. The dual speed focuser is smooth on the course knob, but I feel a slight stepping motion happening on the fine knob. It's not enough to affect focusing, but it isn't what I'd call buttery smooth like some fine focus knobs I've used in the past. The focuser has 8 cm of travel, more than enough to accommodate any eyepiece I tried in the focuser with a 2 inch diagonal. The focuser rotation feature is also appreciated when mounting the scope sideways or even upside-down. The focuser does have a lift issue with heavy loads of 2.5 pounds or more at high angles. I have to push my thumb into the back of the diagonal to get it to pull the load upward, otherwise it just slips. Once in focus, it holds it just fine. I don't know if this tension is adjustable or if adjusting it would make it more difficult to achieve fine focus.

The price is very nice considering everything you get in the package. The case in particular is a nice touch and even has a spot for a 2 inch diagonal. It stores very compactly just about anywhere. It is also nice and short on the mount, creating no vibration dampening issues. It is a little heavy at 5 pounds, but not excessively so. It is very back-end heavy, even more so when you add a large, low power wide field eyepiece for sky scanning. I'm still working out how to best balance it. That heft does give you a reassuring feeling of security when you have an ultra-heavy eyepiece in the focuser. The compression ring really grabs the diagonal and holds it with authority.

Overall, it is a vast improvement over a short-tube 80mm refractor for not a lot more. If this scope had been available 14 years ago, I would never have bought my ST-80 in the first place.
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2. Jim on 5/17/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
Hard to go wrong if this is the kind of scope you are in the market for. Comes with a serviceable case and Astronomics even star tests it before shipment. Fine images from a little, although not exactly lightweight ED refractor. Pretty good build quality for what little you have to pay. If you for some reason decide it is not for you the scope hold its value well and the used market is active. Worth a shot if you ask me.
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3. Paul on 5/16/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
The AT72 is a wonderful telescope. It is great as a grab and go scope. Mine is mounted on a Vixen Port-Mount which makes an ideal combination. And the scope delivers. The stars are pinpoint, the background black, and the power better than one might think given the aperture. I have shot pictures through it (Nikon D5100) with good effect. The stock focuser is smooth and accurate. The scope is well worth the money.
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4. Robbin on 3/12/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
I purchased my AT72ED in October of 2012 while visiting the Astronomics showroom in Norman, Oklahoma. I had already purchased a few eyepieces and as I was getting ready to leave I asked if they had anything that would qualify as a "grab and go" scope. They suggested the AT72ED, so I bought it and took it home that day. It comes in a nice metal case. The scope is well made, has a nice finish and is machined well. It has the look and feel of something costing much more. I was surprised at how crisp the images are. It is perfect for a small grab and go scope, especially for evenings when I only have 30 min to hour to observe. As much as I like my Celestron 8SE, I find myself using the AT72ED as much or more just because it is so quick to set up. The field of views are wide and crisp. I especially like the rotating dual-speed focuser. I use the scope with a simple alt az mount from Celestron which is very light so the whole set up is light and very portable. A friend who has been in the hobby a long time and has owned multiple scopes was very impressed with the quality of and the views provieded by the AT72ED. For the money it is hard to beat. I have been very pleased with this scope and was glad the Astronomics staff recommended it to me.
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Showing comments 1-4 of 4
General Accessories
Altazimuth Mounts (1)
Voyager Altazimuth mount
by Astro-Tech
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$299.00 
Finderscopes (1)
Illuminated multiple reticle finder
by Astro-Tech
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$59.95 
Visual Accessories
Image Erecting Prisms (1)
45° Prism for 1.25" eyepieces
by Astro-Tech
Quantity:  
$59.95 
Miscellaneous (1)
Kit of 1.25" eyepieces and visual accessories
by Astro-Tech
Quantity:  
$129.95 
Star Diagonals (2)
1.25" 99% Reflectivity dielectric mirror diagonal
by Astro-Tech
Quantity:  
$69.95 
2" 99% Reflectivity dielectric mirror diagonal for refractors
by Astro-Tech
Quantity:  
$119.95 
Photographic Accessories
Camera Adapters (1)
2" Prime focus adapter, needs T-ring
by Astro-Tech
Quantity:  
$29.95 
  • Removable combined 1/4”-20 thread mounting foot and equatorial mount dovetail
  • Dust covers
  • Self-storing retractable dew shield
  • Dual speed 2” Crayford focuser with 2” and 1.25” non-marring compression ring accessory holders
  • Fitted aluminum-frame case
  • Dust caps
  • White paint body with black and gray anodized focuser
Documents
Astro-Tech - AT72ED manual 669 KB
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Astro-Tech - AT72ED 72mm f/6 ED doublet refractor, white and gray tube

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Astro-Tech - AT72ED 72mm f/6 ED doublet refractor, white and gray tubeClose-up of the white and gray finish Astro-Tech AT72ED.Close-up of the Astro-Tech AT72ED dual-speed focuser and 1.25Image of the AT72ED fitted hard case.AT72 image of M31, by Tibor Mihalovits. AT72 piggyback on Meade LX200GPS unguided; Astro-Tech field flattener; unmodified Canon T1i; 40 light, 40 flat, 30 dark 90-second exposures.
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The Astro-Tech AT72ED is a worthy successor – and upgrade – to the AT66ED, an Astro-Tech scope that Astronomy magazine called “a product everyone should own.” The AT72ED is optically so good, despite its low price, that you might swear this compact air-spaced ED doublet refractor is an apochromat . . .





. . . our 34th year